The invention relates to a method for rehabilitating an old pipe, in which the outer diameter of a new pipe which at least corresponds to the inner diameter of the old pipe, is initially reduced and the new pipe is then pulled into the old pipe. The invention further relates to a system for carrying out such a method.
A method of the generic type which is also known under the term “swagelining” is for example disclosed in GB 2 218 486 A. In the method disclosed therein, a liner pipe (a so called liner), which is made of a plastic with shape memory, is pulled through a reduction device which has a conically tapered opening whereby the pipe is radially compressed. By this, the diameter of the liner pipe whose outer diameter in the initial state corresponds at least to the inner diameter of the old pipe, is reduced by up to 15%, which enables the liner pipe to be pulled through the old pipe which is laid underground and which is to be lined with the liner pipe with relatively small force. After drawing in the liner pipe into the old pipe the liner pipe is relieved of stress so that the latter expands again due to the shape memory of the plastic and—due to the outer diameter which exceeds the inner diameter of the old pipe—rests against the inner wall of the old pipe under pressure. In this way a gap between the old pipe and the liner pipe can be avoided, which otherwise could undesirably lead to the gap acting as drainage between the old and the liner pipe or being pervaded by roots, which depending on the circumstances can indent the liner pipe and thereby reduce the free flow through.
A problem in the method known from GB 2 218 486 is that this method is only usable for rehabilitation of old pipes whose inner sheath surface is intact and which in particular have no deformed or caved in sections or offsets, as they occur for example in the region of pipe sleeves. Old pipes made of brittle materials, such as for example stoneware or concrete regularly have at least several breaks in which either a part of the sheath is broken or caved in or in which two pipe sections which are separated from one another by a brake form an offset. The method known from GB 2 218 486 A is not regularly usable for such old pipes.